Nowadays, there are increasingly higher safety requirements for vehicles than ever before. At the same time, the comfort of a spacious car interior is also required. Therefore, not only the compactness of an installed airbag is required, but there is also a trend toward downsizing of an inflator which generates an expansion gas, and an airbag capable of fully delivering its performance even with a small amount of gas is becoming necessary. Accordingly, it is necessary to effectively use the gas by preventing the airbag from inflating more than necessary. One example of a bag body related to this requirement is disclosed in Patent Literatures 1 and 2. These are airbags including restriction threads for restricting the distance between base fabrics during inflation of the airbag, and part of the threads constituting one side of the base fabric extends toward the other side of the base fabric and is connected to it.